1. Field of the Invention
The present invention relates to a process for hydrolysing starch to dextrose and particularly concerns an improved process for chromatographic separation of dextrose from starch hydrolysate.
2. The Prior Art
Processes for hydrolysing starch to dextrose have been known for many years and have been subject to a number of modifications and improvements. One aim has been to produce a dextrose product having very high purity either by converting as much of the starch as possible to dextrose to the exclusion of by-products or by providing an efficient method of separating the dextrose from such by-products.
One method of separation of the dextrose is by means of a chromatographic column or bed in which the aqueous starch hydrolysate, suitably after pretreatment such as concentration, filtration and/or decolorization, is absorbed on the column, the by-products passing through the column in the aqueous raffinate. The dextrose is then desorbed by elution with water and the water partially or completely removed to produce a concentrated solution or solid dextrose, the dextrose comprising more than 98% of the dry solids of the solution.
When the chromatographic method of separation is used the dextrose is produced together with the by-products in the aqueous raffinate. This raffinate may contain up to 20 wt % dry solids which may in turn be up to 80 wt % dextrose. The raffinate is usually recycled to an earlier stage in the process but such bulk recycle reduces the plant capacity. The present invention provides a solution to this problem and at the same time gives rise to additional process advantages.